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Outer Membrane Vesicles From Brucella melitensis Modulate Immune Response and Induce Cytoskeleton Rearrangement in

Eric Daniel Avila-Calderón1,2, Olín Medina-Chávez3, Leopoldo Flores-Romo2

  • 1Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, Mexico.

Frontiers in Microbiology
|November 16, 2020
PubMed

Insights

Outer membrane vesicles (OMVs) from smooth and rough Brucella melitensis strains induce immune responses, with LPS presence crucial for OMV stability and immune modulation. These findings offer insights into Brucella pathogenesis and vaccine development.

Area of Science:

  • Microbiology and Immunology
  • Bacterial Pathogenesis
  • Vaccine Development

Background:

  • Brucella melitensis releases outer membrane vesicles (OMVs), which are known to elicit immune responses.
  • Previous studies indicated that OMVs from smooth B. melitensis strains can induce protective immunity.
  • The proteome and immunomodulatory effects of OMVs from the rough B. melitensis VTRM1 mutant were not well-characterized.

Purpose of the Study:

  • To compare the proteomes of OMVs from smooth B. melitensis 16M and its rough mutant VTRM1.
  • To characterize the immune response induced by these OMVs in host cells.
  • To analyze the stability of OMVs from both strains upon treatment with SDS and proteinase K.

Main Methods:

  • Proteomic analysis of OMVs using liquid chromatography-mass spectrometry (LC-MS/MS).
  • Analysis of OMV protein profiles after treatment with proteinase K, sodium deoxycholate, and SDS using SDS-PAGE.
  • In vitro assessment of OMV effects on peripheral blood mononuclear cells (PBMCs), including cytoskeleton, surface molecules, apoptosis, DNA damage, proliferation, and cytokine induction.

Main Results:

  • 131 proteins were identified in OMVs from B. melitensis 16M, and 43 in OMVs from B. melitensis VTRM1.
  • OMVs from the rough mutant (VTRM1) were more sensitive to detergent and enzyme treatment than those from the smooth strain (16M).
  • Both smooth and rough OMVs induced TNFα and IL-6, altered cytoskeleton, and inhibited PD-L1 expression on T-cells, but did not induce IL-17, proliferation, apoptosis, or DNA damage.

Conclusions:

  • Significant proteomic and stability differences exist between OMVs from smooth and rough Brucella strains.
  • The presence or absence of complete O-polysaccharide in LPS is critical for OMV protein protection and immune response modulation.
  • OMVs from both strains demonstrate immunomodulatory potential, impacting cytokine production and T-cell responses, suggesting their utility in understanding Brucella-host interactions and potential vaccine strategies.
Keywords:
BrucellaOMVsbacterial vesiclesextracellular vesicleouter membrane vesiclesproteomics

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